In the transporting or shipment of temperature sensitive materials or items such as blood, plasma, vaccines and certain drugs, it is known to use insulated containers which include heating and/or cooling means as disclosed, for example in U.S. Pat. No. 7,913,511, entitled “Cargo Container for Transporting Temperature Sensitive Items”, and issued Mar. 29, 2011; in U.S. Pat. No. 5,950,450, entitled “Containment System for Transporting and Storing Temperature-Sensitive Materials”, and issued Sep. 14, 1999; in U.S. Pat. No. 5,943,876, entitled “Insulating Vacuum Panel, Use of Such Panel as Insulating Media and Insulated Containers Employing Such Panel”, and issued Aug. 31, 1999; in U.S. Pat. No. 5,483,799, entitled “Temperature Regulated Specimen Transporter”, and issued Jan. 16, 1996; and in U.S. Pat. No. 5,603,220, entitled “Electronically Controlled Container for Storing Temperature Sensitive Material”, and issued Feb. 18, 1997; the disclosures of which are incorporated by reference herein. When it is desirable to transport or ship a larger volume of temperature sensitive items, it is desirable to provide a cargo container which is adapted to receive a pallet supporting the temperature sensitive items and which also includes cooling and/or heating means for maintaining the temperature sensitive items within a close predetermined temperature range. Such cargo containers are disclosed, for example, in U.S. Pat. No. 5,187,947, entitled “Wheel Type Freezer and Method for Rapid, Low Temperature Freezing”, and issued Feb. 23, 1993; and U.S. Pat. No. 6,860,115, entitled “Air-Cargo Container, a Refrigerator Unit for an Air-Cargo Container and a Manufacturing Method of an Air-Cargo Container”, and issued Mar. 1, 2005; and in a publication of applicants entitled AcuTemp™ Thermal Pallet Shipper; the disclosures of which are incorporated by reference herein. A Temperature-Controlled, Pallet-Sized Shipping Container is also disclosed in U.S. Pat. Pub. No. 2004/0226309, published Nov. 18, 2004, and the disclosure of which is herein incorporated by reference. This published application claims the benefit of U.S. Provisional Pat. Appl'n. No. 60/447,987, filed Feb. 17, 2003, and the disclosure of which is incorporated by reference herein.
The temperature sensitive materials or items may be wrapped in a support material during shipment. Such support material may be used to keep the temperature sensitive materials or items on the pallets during shipment. Nevertheless, the support material does not typically provide adequate insulation, and the temperature sensitive materials or items may take on the ambient temperature of the cargo container. The temperature of the cargo unit can significantly fluctuate due to the higher temperatures during the day and the lower temperatures at night or as a result of differing temperatures of various locations and/or elevations during transport and distribution. As a result, the temperature sensitive materials or items are exposed to the fluctuating temperatures of the cargo container, which can adversely affect the temperature sensitive materials or items during storage, transport, and/or distribution. It may therefore be desirable to provide a support material comprising phase-changing materials (“PCM”) to thereby maintain a more constant temperature within the temperature sensitive materials or items.
A PCM is a substance with a high heat of fusion which, by melting and solidifying at a particular temperature, is capable of storing and releasing significant amounts of energy while maintaining a nearly constant temperature. Heat is absorbed or released as the PCM changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage units. In particular, when an external temperature rises, heat is absorbed by the PCM as the PCM changes from solid to liquid to thereby have a cooling effect upon items close to or contacting the PCM; whereas when the external temperature drops, heat is released by the PCM as the PCM changes from liquid to solid to thereby have a heating effect upon items close to or contacting the PCM. The internal temperature of the PCM, however, remains nearly constant as the PCM changes from solid to liquid and vice versa, which is useful for keeping temperature sensitive materials or items at a uniform temperature. A user may “condition” a PCM by heating, cooling, and/or freezing the PCM prior to use to thereby place the PCM in a condition to absorb or release heat at a predetermined/estimated temperature. Some commonly used PCMs include: salt hydrates, paraffin wax, fatty acids, and esters.
PCM packs are generally packaged in individual rigid plastic bottles or flexible plastic pouches. The rigid plastic bottles and flexible plastic pouches typically have no secondary layer of protection and may crack, tear, or become worn upon repeated use thereby causing leakage of the PCM. Therefore, in any cargo container adapted to receive one or more pallets of temperature sensitive materials or items, it may be desirable to provide PCM packs that are durable enough to withstand the inherent hazards of use such as rips, tears, abrasions, etc. It may also be desirable to provide features that allow for simple and efficient packing and/or orientation of the PCM packs within the cargo container. Furthermore, when rigid plastic bottles and/or flexible plastic pouches are used, these types of PCM packs typically require a large quantity of individual packs in order to achieve sufficient product coverage within the cargo container. Thus it may further be desirable to provide features that allow for sufficient coverage of the temperature sensitive materials or items within the cargo container while using the least number of PCM packs possible.
PCM packs that are required to maintain product temperatures within an upper and lower temperature limit will generally include at least two PCMs with different melting and/or boiling points. A first PCM pack will be conditioned in a solid state and will thaw during use to prevent temperatures from exceeding the high end of the temperature range. A second PCM pack will be conditioned in a liquid state and will freeze during use to prevent temperatures from exceeding the low end of the temperature range. For example, a first PCM pack having a freeze point of 0° C. (32° F.) may be conditioned at −20° C. (−4° F.) such that the first PCM pack is in a solid state prior to use in a 2-8° C. (35.6-46.4° F.) environment, while a second PCM pack having a freeze point of 3° C. (37.4° F.) may be conditioned at 5° C. (41° F.) such that the second PCM pack is in a liquid state prior to use in the 2-8° C. (35.6-46.4° F.) environment. A pouch may be provided that is designed to receive multiple PCM packs in those instances where a single conditioning temperature will result in a solid state for a first PCM pack and a liquid state for a second PCM pack. For example, a first PCM pack with a freeze point of 3° C. (37.4° F.) and a second PCM pack with a freeze point of 18° C. (64.4° F.) may be concurrently conditioned at 5° C. (41° F.) prior to use in a 2-25° C. (35.6-77° F.) environment such that the first PCM pack is in a liquid state and such that the second PCM pack is in a solid state.